Greg Pierce's two-character play brings together an uncle and his niece who, through two sets of tragic circumstances, seek refuge in the Costa Rican dry forest, near a tiny town called Los Angeles and a good distance away from the capital city San Jose. It seems an odd vacation spot for a sixteen-year-old until we learn that Becky (Rae Gray) was involved in (and is accused of bearing responsibility for) an accident that resulted from alcohol abuse and teasing of a mentally challenged girl at a house party in Massachusetts. Her trip to Costa Rica turns out to be less a vacation than an escape from the attention of the media, while the legal authorities wait to see if the injured girl (cruelly nicknamed "Slowgirl" by the other kids) recovers and whether or not to press charges. As the play progresses, we learn how the uncle, Sterling (William Petersen), chose to live in such seclusionhe has his reasons for escaping society as well. He's been estranged from the family for years, but his Central American home is such a perfect getaway for Becky that her mother, Sterling's sister, arranges Becky's stay.

A stage appearance by Chicago favorite William Petersen (who began his career here in storefront theater before making it big in TV and movies) is always an occasion. He returns to local stages every two years or so and proves he still has his chops. Petersen has an amazing ability to give performances so subtle and natural that they nonetheless have the intimacy of a film or TV performance. In Slowgirl, his character is a quiet, nearly broken man who maintains only limited contact with others and spends his days reading books or tending to the labyrinth he's built on the mountain above his small house. Sterling has less dialogue than Becky (she's quite a talker), and his sentences are mostly short and filled with monosyllabic words. Petersen masterfully tells us what we need to know about Sterling through physicality: hunched shoulders, halting walk, slight turns of the head or hesitancy in speaking.

His sole castmate in Slowgirl is the young Chicago actress Rae Gray, a University of Chicago student who has an impressive professional resume and has grown up from child actress to leading lady before Chicago audiences' eyes. She's more than able to hold her own with the venerable Petersen. Her Becky is almost nonstop chatterimmature but eventually revealing depths that may not have been apparent back home, plus a capacity for growth that is ultimately surprising given where she starts out at the play's beginning.

The situation feels more than a little contrived. The likelihood that Becky would have been allowed to leave the country under a cloud of criminal culpability seems slim (and in fact, that is acknowledged as such in the script). Sterling's estrangement from his sister (and even more so from her husband, Becky's dad), makes it even less likely that such a visit would have been planned. Pierce seems to openly ask us to accept those improbabilities and listen to his tight, concise tale of the parallel searches for redemption the two characters share.

Director Randall Arney keeps the action moving and engaging for its ninety minutes, even when relatively little is happening on stage. The stage is nearly bareSterling explains that he's taken all the doors and windows off so Takeshi Kata's set design is little more than a frame sitting on a platform in between the two seating areas of the Steppenwolf Upstairs Theatre, now in an alley configuration. The set slides to the left and right to change perspective. Together with Richard Woodbury's sound effects of animal noises, the place is appropriately established.

Both Sterling and Becky are hard to warm up to, but to the credit of Pierce's economical writing and expert acting and direction, we develop compassion for these two. Slowgirl is a modest but moving piece that succeeds in achieving exactly what it set out to do.

Slowgirl will run through August 25, 2013, in the Steppenwolf Upstairs Theatre, 1650 N. Halsted, Chicago. For ticket information visit www.steppenwolf.org, the box office or call 312-335-1650.